Optical components having integrated optical waveguide structures are known. These optical waveguide structures possess a difference in refractive index as compared to the substrate surrounding them, so that they are suitable for guiding light waves. A conventional method is described, for example, in U.S. Pat. No. 5,136,677, in which the chalcogenide glasses are subjected locally to an exposure in order to produce the optical waveguide structure. An exposure occurs here in relatively thin substrates, in the light wave transmission direction of what will later be optical waveguide structures. It is also known from U.S. Pat. No. 5,136,677 that intersecting optical waveguide structures can be created in a substrate using two different light sources, and that the optical properties of the optical waveguide structures can be influenced using interference phenomena.
It is known, in order to allow the optical waveguide structures, once produced, to guide electromagnetic waves, for example light waves, that they must have a refractive index which is typically a few percent higher than the substrate surrounding the optical waveguide structure. In addition, the dimensions for the optical waveguide structures lying perpendicular to the light wave propagation direction must be selected so that they are on the order of the wavelength of the light to be guided, typically from 1 to 10 .mu.m. Using the difference in refractive index between the optical waveguide structure and the substrate, and the dimensions of the optical waveguide structures, it is possible to establish the number of modes of light waves being transmitted for a given wavelength being guided. This defined refractive index difference, with the necessary small dimensions, can be achieved with the conventional methods for the manufacture of optical waveguide structures only at the cost of substantial losses.
The optical waveguide structures are usually produced in integrated optical components which are configured, for example, as amplifiers, splitters, couplers, multiplexers, or switches. For this purpose, optical fibers, for example glass fibers, which feed signals in and out are coupled to the optical waveguide structures in the optical components. The problem arises here that the glass fiber cross section must be coupled to the optical waveguide cross section. The effective cross section for common glass fibers is 5 to 10 .mu.m. With integrated optical components, it is advisable to work with smaller cross sections, for example in order to increase the energy density in the optical waveguide structures or to spatially delimit light guidance so that the physical size of the integrated optical components can be reduced. Because of the difference in cross sections at the coupling point, attention must be paid to the numerical aperture, which describes the angular region from which an optical fiber can accept incident light. Light which is incident at a limit value greater than one corresponding to the numerical aperture cannot be guided, and is lost. On the other hand, the small cross section of the optical waveguide structures in the integrated optical components necessarily results in an increase in the numerical aperture, so that light signals sent out from the integrated optical components can be only partially transferred into the coupled glass fibers.
In order to mitigate this problem and the losses associated therewith, it is known to provide a so-called "taper" between the optical waveguide structures and the glass fibers, as a transitional structure. This is intended to effect a continuous transition for the effective cross sections of the glass fibers and the optical waveguide structures, and for the numerical aperture.
The taper can be only incompletely configured using the conventional manufacturing methods for optical waveguide structures, in which optical waveguide structures are produced in, for example, glass, polymer, or Ormocer substrates or in surface layers of silicon wafers using ion exchange, a local change in the stoichiometry of oxides or oxynitrides, or a local filling of etched or stamped valley structures. Because of the limited depth of the layer thickness, cross-sectional adaptation can be accomplished only by expanding the waveguide cross section while the depth remains the same. The refractive index is often defined by the material properties, and is therefore constant over the entire taper. The result can be that the taper becomes entirely or partially multimodal, i.e. that propagation directions which cannot be received by the adjacent optical waveguide or glass fibers become possible within it.